The proposed work is concerned with the examination of the biogenesis of membrane lipids in Escherichia coli. Studies will be carried out in living organisms to determine the genetic structure of these pathways. Studies in vitro will be concerned with the characterization of the principal enzymes catalyzing key steps in the biosynthetic scheme. Bibliographic references: Hawrot, Edward and Kennedy, Eugene P.: Biogenesis of Membrane Lipids: Mutants of Escherichia coli with Temperature-Sensitive Phosphatidylserine Decarboxylase. Proc. Nat. Acad. Sci. USA, 72, 1112, 1975.